Sandpaper is the name commonly applied to a tough paper coated with ground flint. Glue is used to hold the flint to the surface of the paper. There is considerable difference in the cutting and wearing qualities of the different brands of sandpaper.

For ordinary work the grades 0, 1/2 , 1, 11/2 , are sufficient. For very fine work 00 may be used. No. 2 may be used in rounding corners, edges, etc. Such places should be made quite smooth with the edge tools before using the sandpaper. If your work is to be inspected by an instructor do not use any sandpaper until the piece has been examined and passed. For nearly all small work it is best to hold the paper without a block as shown in Figs. 46 and 47.

On large surfaces and to give a smooth finish to corners and rounded edges a block may be used.

Plane a block to about 41/4 inches long by 21/4 inches wide and 7/8 inch thick. Keep this block for use when required. Blocks of other sizes and shapes may be required for special work. These may be of almost any size or shape but should always be carefully made and the paper very carefully folded around them. Never glue or nail the paper to the block. Fold it so that it 41may be changed in position until the entire surface has been used. Remember that paper which has been used is often better than a fresh piece, and therefore do not throw any paper away until it has been entirely worn out.

Sandpaper often becomes too dry to work properly. If kept where it will not dry out nor become too damp it will work much better. It may be dampened by sprinkling a little water between the sheets and keeping them pressed tightly together for a few days. Always tear the paper carefully with a saw as shown in Fig. 44.